The present invention relates to a spring compressor which is used to axially compress the helical coil springs of an automobile during the servicing thereof, as, for example, when a shock absorber is to be replaced. A number of patents have been addressed to ways of tightening springs.
Canadian Pat. No. 508, 153 and corresponding U.S. Pat. No. 2,652,625 disclose a plate attachment to a jack which allows the force of the jack to be used to partially compress a coil spring in order that a shim can be inserted. Although the jack is suspended by chains, the chains are not used for tightening purposes. Neither is there disclosed a screw thread tightening mechanism.
Canadian Pat. No. 767, 357 and corresponding U.S. Pat. No. 3,341,175 disclose the use of two grippers of a particular design attached by a bolt member which is tightened to compress a spring. U.S. Pat. No. 3,051,433 similarly involves an arrangement having two gripper members and a bolt therebetween; the shape of one of the grippper members differs from that disclosed in the aforesaid two patents.
Canadian Pat. No. 1,049,237 relates to a locking frame which tightens by means of tightening fitted rods. U.S. Pat. No. 3,070,354 discloses the use of a heavily built cage into which the spring is placed and in which it is then compressed.
U.S. Pat. No. 3,087,706 discloses a spring compressor comprising two or three individual compressors. Each compressor includes a shank having a curved hook formation and a threaded spindle section on which a threaded nut is screwed to engage a sleeve. The spring is compressed between the hook on the end of the shank and the hook on the sleeve as the nut is screwed onto the threads of the shank.
U.S. Pat. No. 3,722,862 shows the use of a chain in a jack and lock combination. The compression is effected by means of a jack which is suitably secured to an anchor and is hooked by a hook to the spring. Provision is made for securing the chain against inadvertant slippage in the jack and lock assembly by the use of a blocking pin inserted through aligned holes in the lock.
U.S. Pat. No. 3,764,107 discloses a compressor with pivotally connected jaws adapted to engage the axially spaced coils of a spring. U.S. Pat. No. 4,036,473 also shows a device with two jaws, which extend into the spring from the side; the two jaws are compressed together by pneumatic cylinders.
U.S. Pat. No. 4,061,308 discloses a device having two retainers, with open sides, which are locked by retainer bars. The two retainers are connected by a jack which is used to compress the springs.
U.S. Pat. No. 1,384,969 shows a device comprising a threaded rod with two jaws screwed on it. The threaded rod is then turned so that the jaws move together to compress the spring. U.S. Pat. No. 1,342,529 shows a similar device, but having parallel linkages and a screw to collapse the jaws instead of having the jaws on the screw thread.
U.S. Pat. No. 2,510,334 shows a device for compressing a number of valve springs simultaneously. It uses lever arms and a threaded rod for tightening.
U.S. Pat. No. 3,982,720 discloses a crank-operated compressor member having two arms which move relative to one another to compress the spring. The prior art discussed by this patent discloses a design wherein two threaded rods with hooks on them, and a wing nut to be tightened on each rod, are used to compress a spring.
Patents have also disclosed the use of a chain being hooked about something which is to be pulled. Canadian Pat. No. 269,542 deals with a wheel puller, for use in taking a wheel or gear from a shaft. The wheel puller has chains which fit around the spokes of the wheel and hook into a puller member. The puller member has a screw threaded through it in the centre, and this bears on the shaft of the wheel. As the screw is turned by a wrench, the chains pull the spokes, thereby moving the wheel off the shaft.
It will be seen that the previously disclosed spring compressors are both more complex and more difficult to use than the device herewith disclosed. Furthermore, unlike some compressors which use interchangeable dies and are therefore limited in the number of springs with which they can be used, this compressor is independent of the size of the coil springs. Use of the disclosed compressor does not require that the strut assembly be taken off the car, thus obviating the need for re-assembly and the consequent wheel alignment. The disclosed compressor is capable of being used in the limited spaces often found about automobile coil springs. The disclosed compressor is also very safe as it cannot slip off the spring when the spring is compressed. The disclosed compressor is inexpensive to manufacture and can be easily operated by the mechanic.